High purity polycrystalline silicon, which is used as a raw material for single-crystal silicon for use in semiconductors, is generally produced by a process called the “Siemens process”. In the Siemens process, polycrystalline silicon is produced by a reduction reaction and thermolysis reaction of trichlorosilane (SiHCl3), as shown by the reaction formulas (1) and (2) below.SiHCl3+H2→Si+3HCl   (1)4SiHCl3→Si+3SiCl4+2H2   (2)
Further, trichlorosilane, which is used as a raw material in the Siemens process, can be produced by reacting silicon tetrachloride (SiCl4:tetrachlorosilane) with hydrogen to effect conversion, as shown by the reaction formula (3) below.SiCl4+H2→SiHCl3+HCl   (3)
Conventionally, in the production of polycrystalline silicon by the Siemens process, it is known that the generated reaction gas contains monochlorosilane, dichlorosilane and polymeric silicon chloride compounds referred to as “polymer”, as well as trichlorosilane and silicon tetrachloride (see Patent Document 1). The above-mentioned polymer is a generic term including high-order silicon compounds (polymeric silicon chloride compounds) having two or more silicon atoms, such as Si2Cl6, Si3Cl8 (trisilicon octachloride) and Si2H2Cl4.
A residual liquid obtained by distilling the polymer contains trisilicon octachloride (Si3Cl8), which is a trisilane having three silicon atoms, and tetrasilicon decachloride (Si4Cl10), which is a tetrasilane having four silicon atoms. Conventionally, these silanes were subjected to hydrolysis treatment with water, an alkali, or the like. For example, Patent Document 2 discloses a technique of decomposing the polymer.
[Patent Document 1] International Patent Application Publication No. WO02/012122
[Patent Document 2] Japanese Unexamined Patent Application, First Publication No. Hei 11-253741